A packet of cigarettes is known to be fed through a feed station, where it is applied with a respective sheet of polypropylene overwrapping material, which is folded about the packet into a U- or L-shaped configuration; the packet, together with the respective sheet of overwrapping material, is then fed to a folding station, where the sheet of overwrapping material is folded further about the packet to form a tubular wrapping, which is then stabilized by heat sealing the superimposed lateral portions of the sheet of overwrapping material; and, finally, the tubular wrapping is closed by folding the outer ends of the tubular wrapping onto the packet, and is stabilized by heat sealing the superimposed end portions of the sheet of wrapping material.
Though widely used on machines (known as cellophaning machines) for overwrapping packets of cigarettes, by being easy to implement and permitting high operating speeds, the above wrapping method has been found to result at times in poor-quality overwrapping, by the sheet of overwrapping material about the packet of cigarettes presenting creases which, while not impairing the function of the overwrapping itself, are considered unsightly by consumers.
GB-453165-A1 discloses a wrapping machine of the kind in which an article and a wrapper are moved by an article carrier to a delivery station from a feeding-in station between which and the carrier a wrapper is located, the wrapper being drawn substantially completely around the article during the motion of the latter as it passes from the feeding-in station onto the carrier and to the delivery station. As the article enters the carrier the wrapper is clamped between the article and a backing plunger and is drawn out from under a roll, which serves to keep the wrapper straight irrespective of irregularities in the shape of the article by keeping a proper tension on the wrapper. However, the solution given by GB-453165-A1 for avoiding the formation of creases in the wrapping cannot be implemented in an easy and cheap manner to a modern cellophaning machine for overwrapping packets of cigarettes, due to the high operational speed of such machines.
U.S. Pat. No. 5,305,580-A1 discloses a method of producing tubular wrappings for parallelepiped products or similar, whereby the products and respective portions of wrapping material are fed successively on to a respective first and second conveyor and fed continuously along a common route, along which each portion of wrapping material is transferred on to the first conveyor by a pair of supports supporting a respective product and supported on and moving with the first conveyor, each pair of supports being rotated for wrapping a respective portion of wrapping material about the respective product and so forming a respective tubular wrapping, the opposite portions of which are overlapped and welded together by a welding device assigned to each pair of supports.